The MrgA protein of Bacillus subtilis was originally classified as a Dps(PexB) homologue, encoded by a metalloregulated oxidative-stress gene (metallo regulated gene) mrgA. One purported function of the MrgA protein in B. subtilis is to bind DNA under conditions of oxidative stress and to protect the DNA against damage (Chen L, Helmann J D. 1995. Bacillus subtilis MrgA is a Dps(PexB) homologue: evidence for metalloregulation of an oxidative stress gene. Mol Microbiol 18: 295-300).
A B. subtilis mrgA deletion mutant only had a somewhat reduced overall level of secreted proteins, and it was therefore broadly concluded that MrgA is not involved in protein secretion in B. subtilis, (van Wely K H, Swaving J, Klein M, Freudl R, Driessen A J. 2000. The carboxyl terminus of the Bacillus subtilis SecA is dispensable for protein secretion and viability. Microbiology 146: 2573-81).
However, the present inventors have found, as demonstrated herein, that MrgA is in fact involved in secretion in Bacillus, and that a higher expression of mrgA leads to a higher secretion of an exoenzyme, exemplified below by improved secretion of a heterologous alpha-amylase.